[GitHub/mt8127/android_kernel_alcatel_ttab.git] / Documentation / i2c / ten-bit-addresses

The I2C protocol knows about two kinds of device addresses: normal 7 bit
addresses, and an extended set of 10 bit addresses. The sets of addresses
do not intersect: the 7 bit address 0x10 is not the same as the 10 bit
address 0x10 (though a single device could respond to both of them).

I2C messages to and from 10-bit address devices have a different format.
See the I2C specification for the details.

The current 10 bit address support is minimal. It should work, however
you can expect some problems along the way:
* Not all bus drivers support 10-bit addresses. Some don't because the
  hardware doesn't support them (SMBus doesn't require 10-bit address
  support for example), some don't because nobody bothered adding the
  code (or it's there but not working properly.) Software implementation
  (i2c-algo-bit) is known to work.
* Some optional features do not support 10-bit addresses. This is the
  case of automatic detection and instantiation of devices by their,
  drivers, for example.
* Many user-space packages (for example i2c-tools) lack support for
  10-bit addresses.

Note that 10-bit address devices are still pretty rare, so the limitations
listed above could stay for a long time, maybe even forever if nobody
needs them to be fixed.
Commit	Line	Data
89140f41	1	The I2C protocol knows about two kinds of device addresses: normal 7 bit
1da177e4 LT	2	addresses, and an extended set of 10 bit addresses. The sets of addresses
1da177e4 LT	3	do not intersect: the 7 bit address 0x10 is not the same as the 10 bit
cbb44514	4	address 0x10 (though a single device could respond to both of them).
1da177e4	5
cbb44514 JD	6	I2C messages to and from 10-bit address devices have a different format.
cbb44514 JD	7	See the I2C specification for the details.
1da177e4	8
cbb44514 JD	9	The current 10 bit address support is minimal. It should work, however
	10	you can expect some problems along the way:
	11	* Not all bus drivers support 10-bit addresses. Some don't because the
	12	hardware doesn't support them (SMBus doesn't require 10-bit address
	13	support for example), some don't because nobody bothered adding the
	14	code (or it's there but not working properly.) Software implementation
	15	(i2c-algo-bit) is known to work.
	16	* Some optional features do not support 10-bit addresses. This is the
	17	case of automatic detection and instantiation of devices by their,
	18	drivers, for example.
	19	* Many user-space packages (for example i2c-tools) lack support for
	20	10-bit addresses.
	21
	22	Note that 10-bit address devices are still pretty rare, so the limitations
	23	listed above could stay for a long time, maybe even forever if nobody
	24	needs them to be fixed.